Welding of laminar metallic elements



United States Patent 3,229,364 WELDING 0F LAMINAR METALLIC ELEMENTS Hugh Thomas, Irvine, and William Thornhill Montgomery, Ardrossan, Scotland, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain N0 Drawing. Filed Feb. 25, 1963, SenNo- 260,872 Claims priority, application Great Britain, Mar. 1, I962, 8,036/62 T Claims. (Cl. 29-4743) This invention relates to a new method of welding together laminar metallic elements and -to welded structures formed thereby. f t

According to the present invention a method of welding together metal laminae consists in assembling two or more metal laminae into a laminated assembly in which the surfaces of adjacent laminae are in direct contact, placing a layer of high explosive in proximity over each of the two outer faces of the laminated assembly and detomating the explosive, whereby the laminae are welded together at contacting surfaces.

Welding of the metal results from the action of the intense shock waves released on detonation of the explosive. Two such shock waves are generatedw-hen the explosive is detonated one wave travelling from each layer of explosive These shock waves meet within the laminar assembly and the heat generated by' their collision'is rapidly dissipated within the metal and contributes to the welding process. Detonation of an explosive layer on only one surface of the laminar assembly does not result in satisfactory welding of the laminae.

Any detonating explosive may be used but it is preferable to choose a plastic explosive which can be readily formed into a uniformly thick layer con-forming to the shape of the surface over which it is placed. We have found gelatinous detonating explosives containing gelatinised nitroglycerine and explosives containing pentaerythritoltetranitrate or cyclotrirnethylenetrinitramine mixed with plastic binder to be convenient. Another very convenient explosive for this purpose is commercial detonating fuse consisting of a thin core of pentaerythritoltetranitrate powder surrounded by a Waterproof sheath of synthetic plastic material. This material may be readily placed over the surface to form the required layer and if desired more than one layer of the fuse cord may be employed.

The weight of explosive used per unit of surface area of the metal lamina over which it is placed should preferably be limited ,to an amount which on detonation will not cause excessive surface damage or cracking of the metal. As a safeguard against surface damage We have found it advantageous to place a layer of inert protective material between the explosive layer and the metal surface to attenuate the shock wave and reduce the effective pres sure pulse on the metal surface. Wet cardboard has been found convenient for this purpose. The thicknesses of explosive and protective layers used may be chosen to give the required welding effect while avoiding excessive surface damage. The thickness of the explosive layer required will vary in accordance with the nature of the metal being welded and the thickness of the laminated assembly whereas the thickness of inert material required to protect the surface will vary in accordance with the nature of the outer metal surfaces and the nature and amount of explosive used. The optimum layer thicknesses may be readily obtained by simple experiments.

sitates immersion thereinto of the laminated assembly I with the explosive charges fixed in place. Precautions should preferably be taken to prevent ingress of water between the explosive layer and the metal surface.

Although the invention may be advantageously applied in welding any metals, since it provides a method of rapidly welding two or more coincident metallic layers over a large area of contact, it is of particular advantage in welding these metals to which the conventional method cannot readily be applied. For example metals such as aluminium and titanium, which may be damaged by prolonged heating, may be readily welded. The parts to be welded may be either of the same or different metals.

The invention may advantageously be used to apply a covering layer of one metal on a base layer of another, or to weld a metallic lining into a hollow metallic body the weld being substantially uniform over the entire area of contact. The method is also applicable to seaming together metallic'members by lapping portions of the members, placing an explosive charge on each free surface of the overlapping portion and detonatin-g it. Again this is specially advantageous in forming assembled structures from metals which are difiicult to weld by conventional methods.

The invention also includes welded structures formed by the aforedescribed method.

The invention is further illustrated by the following examples in which cleaned metal plates were assembled in a laminated assembly, both the free surfaces were covered with a layer of wet greyboard and a layer of explosive was placed over each layer of greyboard. The assembly was firmly tied together by means of adhesive tape placed in a thin polythene bag and immersed in water. Finally the explosive was detonated. For convenience and clarity the details of the examples are set forth below in tabular form. The metal plates used were in all cases 3 millimetres thick except in Examples 14 and 15 where a sheet of aluminium foil 0.02 millimetre thick was placed between two other plates. The greyboard was used in sheets 2 millimetres thick, multiple layers being used in some examples as indicated.

The plastic explosive used in Example 3 was parts powdered pentaerythr-itoltetranitrate mixed with 30 parts of a binding composition containing 4 parts of nitrocellulose, 3 parts of dibutylphthalate and 23 parts of a dinitrotoluene oil, all parts being by weight.

The detonating fuse used in the remaining examples had a core of powdered pentaerythritoltetranitrate (*PETN) 2.5 millimetres in diameter surrounded by a sheath of plasticised polyvinylchloride. The overall diameter of the fuse was 4.75 millimetres and the PETN charge was approximately 3 grams per foot of fuse.

After detonation of the explosive the joints formed between the metal surfaces were subjected to visual and metallurgical tests to determine whether welding had occurred uniformly over the surface and the results of these tests are given in the final column of the table. In all the examples a uniform weld was obtained between the contacting surfaces of the plates.

TABLE Dimensions Explosive Charge on each surface Number E 1 Metals 111 laglnnated of (slonftaetin griayboard R H xamp e assem y uraces Description and Loading ayers esu (centimetre) assembly used 1 Aluminum-Aluminum x 5 1 lfayer detonating 0. 1 1 Uniform weld.

use.

2 "do 5 x 5 2 lfayer detonating 0.2 4 Do.

use.

do 5 x 5 3 millimetre thick 0. 47 1 Uniform weld layer of plastic but final strucexplosive. ture somewhat distorted.

4 do x 1 layer detonating 0. 1 1 Uniform weld. fuse. Slight distortion of welded structure.

15 x 20 2 lfayers detonating 0. 2 4 Uniform weld.

use. Copper-Copper 5 x 5 .do 0.2 1 Do. Titanium-Titanium 5 x 5 -do 0. 2 1 D0. Stainless steel-Stainless steel- 5 x 5 4 ltayers detonating 0. 4 1 Do.

use. Brass-Aluminum 5 x 5 2 layers detonating 0. 2 1 Do.

use. Copper-Mild Steel 5 x 5 4 liayers detonating 0. 4 1 Do use. Aluminum-Mild steel 5 x 5 2 lfayers detonating 0. 2 1 Do.

use. Aluminum-stainless steel 5 x 5 do 0. 2 1 Do. O0pper-AluminuJn-Brass 5 x 5 do 0. 2 1 Uniform weld at both joints.

Brass-Aluminum foil-Brass" 5 x 5 4 layers detonating 0. 4 1 Do.

use. Aluminum-Aluminum 5 x 5 2 layers detonating 0. 2 1 Do.

Foil-Stainless steel. fuse.

What we claim is: a

1. A method of welding together metal laminae comprising: assembling two metal laminae with the surface of each lamina in direct contact with substantially the entire opposed surface of the other lamina and welding together the engaged surfaces at least partially by heat generated by colliding shock waves, said welding being effected by placing a layer of high explosive in proximity over each of the outer surfaces of the assembly, the layers of explosive having the same velocity of detonation and being equispaced from the plane of engagement of the metal surfaces, and detonating the explosive layers simultaneously.

2. A method of welding in accordance with claim 1 wherein the high explosive is a plastic explosive.

3. A method of welding in accordance with claim 2 wherein the plastic explosive is one containing gelatinised nitroglycerine.

4. A method of welding in accordance with claim 2 wherein the plastic explosive is mixed with a plastic binder and is selected from the group consisting of pentaerythritoltetranitrate and cyclotrirnethylenetrinitramine.

5. A method of welding in accordance with claim 1 wherein the high explosive is detonating fuse consisting of a thin core of pentaerythritoltetranitrate surrounded by i a waterproof sheath of synthetic plastic material.

6. A method of welding in accordance with claim 1 3O wherein a layer of inert protective material is placed between the explosive layer and the metal surface.

7. A method of welding in accordance with claim 1 wherein the high explosive layer is confined by a stemming material.

claim 1.

References Cited by the Examiner UNITED STATES PATENTS Taylor et al.

Williams 29-421 Kaempen 2947l.1 Cowan et a1 294-87 XR JOHN F, CAMPBELL Primary Examiner, 

1. A METHOD OF WELDING TOGETHER METAL LAMINAE COMPRISING: ASSEMBLING TWO METAL LAMINAE WITH THE SURFACE OF EACH LAMINA IN DIRECT CONTACT WITH SUBSTANTIALLY THE ENTIRE OPPOSED SURFACE OF THE OTHER LAMINA AND WELDING TOGETHER THE ENGAGED SURFACES AT LEAST PARTIALLY BY HEAT GENERATED BY COLLIDING SHOCK WAVES, SAID KWELDING BEING EFFECTED BY PLACING A LAYER OF HIGH EXPLOSIVE IN PROXIMITY OVER EACH OF THE OUTER SURFACES OF THE ASSEMBLY, THE LAYERS OF EXPLOSIVE HAVING THE SAME VELOCITY OF KDETONATION AND BEING EQUISPACED FROM THE PLANE OF ENGAGEMENT OF THE METAL SURFACES, AND DETONATING THE EXPLOSIVE LAYERS SIMULTANEOUSLY. 